This invention relates to an improvement on the parts exchanging device for blow molding apparatus, particularly to a counter measure to shorten time required for exchanging parts and the construction of a carrier.
Conventionally, in the case where tubular plastic articles, such as plastic containers, are blow molded, parison pushed out of an extrusion head is caught by a mold of a blow molding apparatus and the air is let in the parison by working air blowing means comprising a pre-pinchers, an air nozzle, etc., arranged below the mold.
When exchanging molds, a die and a core attached to an extrusion head (hereinafter referred to as "a die/core attachment"), must also be exchanged and when exchanging the die/core attachment, a carrier is moved between below the die/core attachment fitting position at the extrusion head and the die/core attachment carrying in and out position so as to exchange an old die/core attachment with a new one by detaching an old one and attaching a new one in relation to the extrusion head by a detaching and attaching device mounted on the carrier.
In the above conventional method, however, whenever a new and old die/core attachments are exchanged, the carrier must run twice between below the die/core attachment fitting position at the extrusion head and the die/core attachment carrying in and out position and also transferring of die/core attachments must be made by the operation of a crane. Thus, it has been a problem that many hours are required for exchanging of die/core attachments.
On the other hand, in the field of the conventional blow molding apparatus automation has been planned and the precision of apparatus itself has been taken into consideration in construction. Therefore, in order to avoid existence of any impedance which can impede movement of the carrier between the die/core attachment fitting position and the die/core attachment carrying in and out position when the die/core attachments are exchanged, for example, various contrivances have been made, for instance, detouring an impedance which can impede movement of the carrier below rails of the carrier and improving the construction of blow molding apparatus itself.
However, there is a limit in avoiding existence of impedances which can impede movement of the carrier on its moving locus and moreover it is troublesome to do so. Thus, it has been required to avoid effectively impedances which can impede movements of the carrier.